One interesting idea that is almost a default in the question is that 40 hours is the bare minimum to get a job done and you go above and beyond that often to succeed.
I think it would be great if we also encouraged efficiency. For example, in graduate school, I knew people that would spend 20 hours over a weekend at the library studying for a test. But a lot of that time they are checking Facebook, relaxing, drifting off. And I would often come in and crank it out. 2 sessions of 3-4 hours each. A lot less time but actually did better.
What if the same could be true at work? Instead of hours focusing on efficiency…remember the great messages of the 60s that with all the amazing technology we’d be working 30 hours a week by the 90s.